1. Field of the Invention
The present invention relates to a sheet processing apparatus utilized as, e.g., banking equipment.
2. Description of the Related Art
As a sheet processing apparatus, there is known a processing apparatus which is used for, e.g., discrimination of the denomination, discrimination of any damage, counting, discrimination of the authenticity, and the like of banknotes. A processing apparatus of this type generally has a banknote supply section in which banknotes to be processed are set, a discriminating section for discriminating the denomination, damage, and authenticity of banknotes supplied from the supply section, and for counting of the banknotes, a sorting section for sorting banknotes in accordance with the discrimination result, and a totaling section for storing the sorted banknotes.
The supply section has pick-up rollers for separating and feeding a banknote, and feed rollers and gate rollers for feeding the picked-up banknote. These rollers are made of an elastic member, e.g., rubber. Of a large number of banknotes set in the supply section, the lowermost banknote is picked up by the pick-up rollers and passed through the gap defined between the feed rollers and the gate rollers. When passing through the gap, banknotes following the first one that are picked up together with the lowermost banknote are stopped and separated from the lowermost banknote by the stopped or reversed gate rollers. Only one banknote is guided to a convey path by the feed rollers and sent to the storing section through the discriminating section.
The physical properties, e.g., the coefficient of friction, the rigidity, and the thickness, of a banknote largely change depending on the ambient environment or the influence of the usage period.
In one proposed arrangement, roller driving mechanisms are incorporated in the gate rollers so that the size of the gap between the feed rollers and the gate rollers can be adjusted. Hence, various types of banknotes set in the supply section can be stably fed even under complicated conditions. Also, even when a change occurs in the surface states of the respective rollers, e.g., a change in the coefficient of friction caused by wear or deterioration over time of rubber, it will not become difficult to reliably feed the banknotes one by one.
More specifically, a pair of sensors each having light-emitting and light-receiving portions are provided on the right and left sides of the convey path in the convey direction. A time required after a feed start reference signal is generated until a banknote blocks the optical path of either sensor and a time required after one sensor is blocked by a banknote until the other sensor is blocked are measured. Based on the time difference between these two measured times, convey information, e.g., pitch variations (variations in time required for feeding banknotes) or skew of banknotes conveyed along the convey path, is detected.
The gate rollers are slightly moved upward or downward based on the convey information, so that the size of the gap defined between the fed rollers and the gate rollers is adjusted. Then, each banknote conveyed along the convey path is fed in an optimum state.
In the detecting method described above, however, when a corner of a banknote is bent or an edge of a banknote is torn, the convey information, e.g., pitch variations or skew of the banknote may be undesirably erroneously detected. If the gap is adjusted based on the erroneous information, it is more likely that a banknote jam undesirably occurs or more than one banknotes are undesirably fed simultaneously.
Japanese Patent Application KOKAI Publication No. 58-96209 discloses an apparatus wherein a line sensor is arranged in a direction perpendicular to a feeding direction of the sheets and scans the sheet in a direction perpendicular to the feeding direction. Based on the detection results of the line sensor, a CPU detects a first skew amount of a side edge of the sheet extending in the feeding direction and a second skew amount of the opposite side edge of the sheet, and compares the first and second skew amount with each other. Then, the CPU selects smaller one of the first and second skew amount as a final skew amount and controls the feeding state of the sheets based on the selected skew amount.
The above-mentioned apparatus can distinguish between a sheet which is being skewed and deformed and a sheet which is being skewed but not deformed. However, since the apparatus selects smaller one of the first and second skew amount, it may erroneously judge the skew amount of the sheet when the sheet is being skewed and deformed.
Further, it is necessary to used a line sensor for scanning the sheets, causing manufacturing cost of the skew detecting device increase.